The visual field of a human eye is the area simultaneously visible to one eye without movement. This area is also known as the peripheral or indirect vision and is the area that surrounds the central or direct vision. More technically, the peripheral vision is that which results from retinal stimulation beyond the macula. Additionally, color perception is closely related to visual acuity for objects. In a similar way that vision decreases as it approaches the perimeter of the visual field, so does the color sense become lessened. As the outer perimeter of the visual field is approached, partial color blindness is followed by a space where the entire color sense is lacking. The variation in this peripheral field, for the several colors, gives rise to perimetry. It is with the measurement of the behavior of these peripheral portions of the retina that this invention is concerned with.
Generally speaking, perimetry takes a visual field by fixating a patient's eye in its central vision while introducing stimuli targets of light in the peripheral vision. By presenting large numbers of light stimuli throughout the visual field and recording the patient's reaction to these stimuli, a mapping of the visual field may be obtained.
It is particularly important to obtain visual field mappings when diagnosing and treating diseases which affect the visual field, such as glaucoma. Currently, most visual field mappings are obtained by machines. These machines are called automated visual field perimeters or computerized perimeters. These machines present light stimuli or targets, monitor the central vision fixation, record the reaction to targets, and map the visual field.